1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer for writing and a method of manufacturing the head.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
One of factors which determine the performances of the recording head is throat height (TH). The throat height is a length (height) from the air bearing surface to the edge of an insulating layer for electrically isolating a thin film coil for generating a magnetic flux. The air bearing surface is a surface of a thin film magnetic head, which faces a magnetic recording medium and is also called a track surface. In order to improve the performances of the recording head, reduction in throat height is desired. The throat height is controlled by a polishing amount at the time of processing the air bearing surface.
In order to improve the recording density in the performances of the recording head, it is necessary to increase track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Referring to FIGS. 58 to 63, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described.
According to the manufacturing method, first, as shown in FIG. 58, an insulating layer 102 made of, for example, alumina (Al2O3) is deposited in thickness of about 5 to 10 xcexcm on a substrate 101 made of altic (Al2O3. TiC) or the like. Subsequently, a lower shield layer 103 for a reproducing head is formed on the insulating layer 102. For example, alumina is then deposited by sputtering in thickness of 100 to 200 nm on the lower shield layer 103 to form a shield gap film 104. An MR film 105 for constructing an MR device for reproduction is deposited in thickness of tens nm on the shield gap film 104 and is patterned in a desired shape by high-precision photolithography. Then lead layers (not shown) as lead electrode layers which are electrically connected to the MR film 105 are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104, and the MR film 105, and the MR film 105 is buried in the shield gap films 104 and 106. An upper shield-cum-bottom pole (hereinbelow, referred to as a bottom pole) 107 made of a magnetic material such as Permalloy (NiFe) used for both of the reproducing head and the recording head is formed on the shield gap film 106.
As shown in FIG. 59, on the bottom pole 107, a write gap layer 108 made of an insulating material such as alumina is formed. Further, a photoresist layer 109 is formed in a predetermined pattern on the write gap film 108 by high-precision photolithography. On the photoresist layer 109, a first thin film coil 110 for an inductive recording head made of, for example, copper (Cu) is formed by plating or the like. A photoresist layer 111 is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist layer 109 and the coil 110. In order to flatten the coil 110 and insulate turns of the coil 110 from each other, a heat treatment is performed at, for example, 250xc2x0 C. A second thin film coil 112 made of copper or the like is formed on the photoresist layer 111 by, for example, plating. A photoresist layer 113 is formed in a predetermined pattern by high-precision photolithography on the photoresist layer 111 and the coil 112. In order to flatten the coil 112 and insulate turns of the coil 112, a heat treatment is performed at, for example, 250xc2x0 C.
As shown in FIG. 60, in a position rearward of the coils 110 and 112 (right side in FIG. 60), an opening 108A is formed by partially etching the write gap layer 108 in order to form a magnetic path. A top yoke-cum-top magnetic pole (hereinbelow, called top pole) 114 made of a magnetic material such as Permalloy for the recording material is selectively formed on the write gap layer 108 and photoresist layers 109, 111 and 113. The top magnetic pole 114 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108A. The top magnetic pole 114 is used as a mask and the write gap layer 108 and the bottom pole 107 are etched about 0.5 xcexcm by ion milling. After that, an overcoat layer 115 made of, for example, alumina is formed on the top pole 114. Finally, a slider is machined to thereby form a track surface (air bearing surface) 120 of the recording head and the reproducing head. In such a manner, a thin film magnetic head is completed.
FIGS. 61 to 63 show the structure of the thin film magnetic head in a completed state. FIG. 61 is a cross section of the thin film magnetic head perpendicular to the air bearing surface 120. FIG. 62 is an enlarged cross section parallel to the air bearing surface 120 of the pole part. FIG. 63 is a plan view. Each of FIGS. 58 to 61 is a cross section taken along line A-AA of FIG. 63. In FIGS. 61 to 63, the overcoat layer 115 is not shown.
In order to improve the performances of the thin film magnetic head, it is important to form the head with accurate throat height TH, apex angle xcex8, pole width P2W and pole length P2L shown in FIGS. 61 and 62. The apex angle xcex8 is an angle formed between a straight line connecting corners of side faces on the track face side of the photoresist layers 109, 111 and 113 and the top face of the top pole 114. The pole width P2W defines the width of a recording track on a recording medium. The pole length P2L indicates the thickness of the pole. In FIGS. 61 and 63, xe2x80x9cTH0 positionxe2x80x9d denotes the edge on the track face side of the photoresist layer 109 as an insulating layer which electrically isolates the thin film coils 110 and 112, that is, a reference position 0 of the throat height TH.
As shown in FIG. 62, a structure in which side walls of the top pole 114, the write gap layer 108 and a part of the bottom pole 107 are formed vertically in a self-aligned manner is called a trim structure. According to the trim structure, an increase in the effective track width due to expansion of the magnetic flux which occurs at the time of writing data to a narrow track can be prevented. As shown in FIG. 62, lead layers 121 as a lead electrode layer electrically connected to the MR film 105 are provided on both sides of the MR film 105. In FIGS. 58 to 61, the lead layers 121 are omitted.
FIG. 64 shows the structure in plan view of the top pole 114. As shown in the diagram, the top pole 114 has a yoke 114A which occupies a major part of the top pole 114 and a pole tip 114B having an almost constant width W1 as the pole width P2W. In the connecting portion between the yoke 114A and the pole tip 114B, the outer periphery of the yoke 114A forms an angle xcex1 to a plane parallel to the air bearing surface 120. In the coupling portion, the outer periphery of the pole tip 114B forms an angle xcex2 to a plane parallel to the air bearing surface 120. For example, xcex2 is about 45 degrees and xcex2 is about 90 degrees. The width of the pole tip 114B specifies the width of a recording track on a recording medium. The pole tip 114B includes a portion F on the front side (the air bearing surface 120 side) with respect to the position TH0 and a portion R on the rear side (on the yoke 114A side) with respect to the position TH0. As understood from FIG. 61, the portion F extends on the flat write gap layer 108, and the portion R and the yoke 114A extend on a coil portion which is covered with the photoresist layers 109, 111 and 113 and is raised like a mountain (hereinbelow, called an apex portion).
The shape of the top pole is described in, for example, Japanese Unexamined Patent Application No. 8-249614.
Since the pole width P2W determines the track width of the recording head, accurate formation is required. Especially, in recent years, in order to realize high surface density recording, that is, to form a recording head of a narrow track structure, a microprocess of setting the width P2W of the top pole to 1.0 xcexcm or less is requested.
As a method of forming the top pole, for example, as disclosed in Japanese Unexamined Patent Application No. 7-262519, a frame plating method is used. In the case of forming the top pole 114 by using the frame plating method, first, a thin electrode film made of, for example, Permalloy is deposited on the whole apex portion by sputtering or the like. A photoresist is then applied on the electrode film and is patterned by a photolithography process to form a frame (outer frame) for plating. By using the electrode film formed before as a seed layer, the top pole 114 is formed by plating.
There is a level difference of, for example, about 7 to 10 xcexcm between the apex portion and the other portion. A photoresist is applied on the apex portion in thickness of 3 to 4 xcexcm. When it is assumed that at least 3 xcexcm of thickness of the photoresist on the apex portion is necessary, since the photoresist having fluidity gathers in the lower part, a photoresist film in thickness of about 8 to 10 xcexcm is formed below the apex portion.
In order to form a narrow track as described above, it is necessary to form a frame pattern having a width of about 1.0 xcexcm by a photoresist film. That is, a fine pattern having a width of 1.0 xcexcm or less has to be formed by a photoresist film having a thickness of 8 to 10 xcexcm or more. It is, however, extremely difficult to form such a thick photoresist pattern in width of the narrower pattern in a manufacturing process.
Moreover, at the exposure time of photolithography, light for exposure is reflected by an electrode underlayer as a seed layer. The photoresist also senses the reflection light, so that a deformation or the like occurs in the photoresist pattern and a sharp and accurate photoresist pattern cannot be obtained. As a result, the top pole cannot be formed in a desired shape in such a manner that the shape of the side walls of the top pole is rounded or the like. Particularly, when the pole width P2W is further reduced to W1A as shown in FIG. 65, it becomes more difficult to obtain the desired width W1A for the following reason. In the portion R extending over the apex portion of the pole tip 114B, the light reflected by the electrode underlayer includes not only reflection light in the vertical direction but also reflection light in the oblique or lateral direction from an inclined face of the apex portion. The reflection light exerts an influence on photosensitivity of the photoresist layer. As a result, the width of the photoresist pattern which defines the pole width P2W becomes wider than an expected value and the shape becomes as shown by broken lines in FIG. 65. In the pole tip 114B, the width of the front portion F with respect to the TH0 position is an extremely important factor of defining the track width on a recording medium. When the width of the portion F becomes wider than W1A, a target fine track width cannot be obtained.
The above-mentioned magnetic head disclosed in Japanese Unexamined Patent Application No. 8-249614 also has a similar problem. In the magnetic head disclosed in the publication, the width of the magnetic pole changes gently from the TH0 position toward the yoke. Consequently, due to an influence of reflection light in the oblique or lateral direction from the inclined face of the apex portion exerted on the photosensitivity of the photoresist layer, the width of the front portion with respect to the TH0 position cannot be accurately controlled.
As shown in FIG. 65, since the portion R from the TH0 position to the connection with the yoke 114A in the pole tip 114B has almost the same width as that of the front portion F with respect to the TH0 position and the cross sectional area of the portion R is small, the magnetic flux from the yoke 114A is saturated in the portion R and cannot sufficiently reach the portion F which defines the track width. As a result, the overwrite characteristic, that is, a characteristic in the case of overwriting data on a recording medium on which data has been already written becomes as low as about 10 to 20 dB. There is a problem such that a sufficient overwrite characteristic cannot be assured.
The invention has been achieved in consideration of the problems and its object is to provide a thin film magnetic head in which the pole width can be accurately controlled and a sufficient overwrite characteristic can be obtained even when the pole width is reduced and to provide a method of manufacturing the head.
According to the invention, there is provided a thin film magnetic head including: two magnetic layers magnetically coupled to each other and two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium;a thin film coil provided between the two magnetic layers; and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein at least one of the two magnetic layers includes: a first magnetic portion for propagating a magnetic flux generated in response to a current passing through the thin film coil, and a second magnetic portion magnetically coupled to the first magnetic portion, and the second magnetic portion includes: a track width defining portion extending with a constant width in the longitudinal direction so as to be apart from a recording-medium-facing surface and defines a recording track width of the recording medium; two or more connection portions magnetically coupled to the first magnetic portion and arranged so as to be separated from each other in the direction of the recording track width; and an intermediate coupling portion having an edge that defines the edge on the recording-medium-facing surface side of the insulating layer and magnetically coupling the track width defining portion and the two or more connection portions.
According to the invention, there is provided a method of manufacturing a thin film magnetic head including: two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between in part close to a recording-medium-facing surface facing a recording medium; a thin film coil provided between the two magnetic layers; and an insulating layers for insulating the thin film coil from the two magnetic layers, the method comprising the steps of forming at least one of the two magnetic layers so as to include a first magnetic portion for propagating a magnetic flux generated in response to a current passing through the thin film coil, and a second magnetic portion magnetically coupled to the first magnetic portion; wherein the step of forming the second magnetic portion includes a track width defining portion which extends in constant width in the longitudinal direction so as to be apart from a recording-medium-facing surface which faces a recording medium and defines a recording tack width of the recording medium, two connection portions which are magnetically coupled to the first magnetic portion and are disposed so as to be separated from each other in the direction of the recording track width, and an intermediate coupling portion which has an edge portion that defines the edge on the recording-medium-facing surface side of the insulating layer and magnetically couples the track width defining portion and the two or more connection portions.
In the thin film magnetic head of the invention, in the second magnetic portion, the recording track width of a recording medium is defined by the track width defining portion, the edge on the side of a recording-medium-facing surface of the insulating layer is defined by an edge of the intermediate coupling portion, and the first magnetic portion is magnetically coupled to the second magnetic portion via the two or more connection portions which are disposed so as to be separated from each other in the track width direction. A magnetic flux generated by the thin film coil passes from the first magnetic portion to the intermediate coupling portion via the two or more connection portions in the second magnetic portion and further to the track width defining portion and reaches the front end portion.
In the thin film magnetic head of the invention, at least one of the two magnetic layers is formed so as to have the first magnetic portion for propagating the magnetic flux generated in response to a current passing through the thin film coil, and the second magnetic portion magnetically coupled to the first magnetic portion. The second magnetic portion is formed so as to include: the track width defining portion extending with a constant width in the longitudinal direction so as to be apart from a recording-medium-facing surface and defines a recording track width of the recording medium; two or more connection portions magnetically coupled to the first magnetic portion and so as to be separated from each other in the direction of the recording track width; and an intermediate coupling portion having an edge that defines the edge on the recording-medium-facing surface side of the insulating layer and magnetically coupling the track width defining portion and the two or more connection portions.
In the thin film magnetic head of the invention or the method manufacturing the same, preferably, a magnetic flux permissible volume of the intermediate coupling portion is smaller than that of the two or more connection portions and a magnetic flux permissible volume of the track width defining portion is smaller than that of the intermediate coupling portion in the second magnetic portion.
In the thin film magnetic head of the invention or the method of manufacturing the same, length in the longitudinal direction of the two or more connection portions of the second magnetic portion may be longer than that of the track width defining portion or the intermediate coupling portion.
In the thin film magnetic head of the invention or the method of manufacturing the same, preferably, the width of the intermediate coupling portion in the position where the intermediate coupling portion in the second magnetic portion and the two or more connection portions are coupled to each other is narrower than the width of a connection region defined by the two or more connection portions.
In the thin film magnetic head of the invention or the method of manufacturing the same, the intermediate coupling portion in the second magnetic portion may include at least one of a portion having a constant width irrespective of positions and a portion having a width which varies according to positions. The two or more connection portions in the second magnetic portion may include at least one of a constant width portion and a varying width portion, the constant width portion having a constant width irrespective of positions, and the varying width portion having a width which varies according to positions.
In the thin film magnetic head of the invention or the method of manufacturing the same, a step in the width direction may be formed in a position where the track width defining portion and the intermediate coupling portion in the second magnetic portion are coupled to each other in such a manner that the width of the track width defining portion is narrower than the width of the intermediate coupling portion in the coupling position. In this case, a step face of the intermediate coupling portion in the step may be substantially perpendicular to the extending direction of the track width defining portion.
In the thin film magnetic head of the invention or the method of manufacturing the same, it is preferable that the width of a region surrounded by the edge portion of the intermediate coupling portion and the two or more connection portions in the second magnetic portion is equal to or wider than the width of the track width defining portion.
In the thin film magnetic head of the invention or the method of manufacturing the same, the edge portion may have an edge face sandwiched by the two or more connection portions and the two or more connection portions may have notches recessed in the width direction at both ends of the edge face.
In the thin film magnetic head of the invention or the method of manufacturing the same, the second magnetic portion may have notches recessed in the longitudinal direction in the position where the track width defining portion and the intermediate coupling portion are coupled to each other.
In the thin film magnetic head of the invention or the method of manufacturing the same, the first magnetic portion may includes a portion having a plane outline corresponding to that of at least either the intermediate coupling portion or the two or more connection portions of the second magnetic portion.
In the thin film magnetic head of the invention or the method of manufacturing the same, a part of the first magnetic portion a part of the second magnetic portion overlap one another.
In the thin film magnetic head of the invention or the method of manufacturing the same, the first magnetic portion may have: a constant width portion which extends from an edge thereof close to the recording-medium-facing surface in a direction of going away from the recording-medium-facing surface with an almost constant width irrespective of positions; and a portion which is coupled to the constant width portion and expands in the width direction as going away from the recording-medium-facing surface.
In the thin film magnetic head of the invention or the method of manufacturing the same, the first magnetic portion may have a portion which extends from an edge thereof close to the recording-medium-facing surface in a direction of going away from the recording-medium-facing surface and expands in the width direction as going away from the recording-medium-facing surface.
In the thin film magnetic head or the method of manufacturing the same, the one of the magnetic layers may further comprise: a third magnetic portion sandwiched between the first and second magnetic portions to make the first and second magnetic portions be magnetically coupled to each other. In this case, it is preferable that the third magnetic portion is arranged so as to overlap with both a part of the first magnetic portion and a part of the second magnetic portion.
In the thin film magnetic head of the invention or the method of manufacturing the same, an edge close to the recording-medium-facing surface of the third magnetic portion may be closer to the side of the recording-medium-facing surface rather than to an edge closer to the recording-medium-facing surface of the first magnetic portion.
In the method of manufacturing a thin film magnetic head of the invention, the track width defining portion, the intermediate coupling portion and the two or more connection portions in the second magnetic portion can be integrally formed by the same process.
In the method of manufacturing a thin film magnetic head of the invention, the track width defining portion and the intermediate coupling portion may be integrally formed by the same process and, subsequently, the two or more connection portions may be formed by a process different from the process of forming the track width defining portion and the intermediate coupling portion.
In the method of manufacturing a thin film magnetic head of the invention, the first magnetic portion may be formed separately from the first magnetic portion by a process different from the process of forming the second magnetic portion.
In the method of manufacturing a thin film magnetic head of the invention, a third magnetic portion may be formed separately from the first and second magnetic portion by a process different from the process of forming the first and second magnetic portions.
Other and further objects, features and advantages of the invention will appear more fully from the following description.